Heart disease, specifically coronary artery disease, is a major cause of death, disability, and healthcare expense in the United States and other industrialized countries. A number of methods and devices for treating coronary heart disease have been developed, some of which are specifically designed to treat the complications resulting from atherosclerosis and other forms of coronary arterial narrowing.
One method for treating such conditions is percutaneous transluminal coronary angioplasty (PTCA). Generally, PTCA is a procedure that involves passing a balloon catheter over a guidewire to a stenosis with the aid of a guide catheter. The stenosis may be the result of a lesion such as a plaque or thrombus. The guidewire extends from a remote incision to the site of the stenosis, and typically across the lesion. The balloon catheter is passed over the guidewire, and ultimately positioned across the lesion. Once the balloon catheter is appropriately positioned across the lesion, e.g., under fluoroscopic guidance, the balloon is inflated to break-up the plaque of the stenosis to thereby increase the vessel cross-section. The balloon is then deflated and withdrawn over the guidewire into the guide catheter to be removed from the body of the patient. In many cases, a stent or other prosthesis must be implanted to provide permanent support for the vessel. Stent prostheses are known for implantation within body lumens to provide artificial radial support to the wall tissue, which forms the various lumens within the body, and often more specifically, for implantation within the blood vessels of the body. Stents are typically constructed of a metal or polymer and are generally a hollow cylindrical shape. When such a device is to be implanted, a balloon catheter, typically carrying a stent on its balloon, is deployed to the site of the stenosis. The balloon and accompanying stent are positioned at the location of the stenosis, and the balloon is inflated to circumferentially expand and thereby implant the stent. Thereafter, the balloon is deflated and the catheter and the guidewire are withdrawn from the patient.
Recently, flexible stented valve prostheses and various delivery devices have been developed so that replacement valves can be delivered transvenously using a catheter-based delivery system. These stented valves may include a collapsible valve attached to the interior of a tubular frame or stent. The stented valves may also have a tubular portion or “stent graft” that can be attached to the interior or exterior of the stent to provide a generally tubular internal passage for the flow of blood when the leaflets are open. The graft can be separate from the valve and it can be made from any suitable biocompatible material including, but not limited to, fabric, a homograft, porcine vessels, bovine vessels, and equine vessels. The stent portion of the device can be reduced in diameter, mounted on a catheter, and advanced through the circulatory system of the patient. The stent portion can be either self-expanding or balloon expandable. In either case, the stented valve can be positioned at the delivery site, where the stent portion is expanded against the wall of a previously implanted prostheses or a native vessel to hold the valve firmly in place. The valve survives the compression and subsequent expansion in fully working form. One embodiment of a stented valve is disclosed in U.S. Pat. No. 5,957,949 titled “Percutaneous Placement Valve Stent” to Leonhardt et al., the contents of which are incorporated by reference herein in its entirety. Although the valve may later require replacement, the patient may receive multiple replacement valves using the minimally invasive catheter method rather than requiring further invasive surgery.
Stents prostheses, including those used in percutaneous heart valve applications, often do not have vessel fixation properties other than providing a coaxial interference fit into the target vessel or location. It is thus an object of the present invention to improve stent retention within a body lumen.